[PATCH] alpha smp fix

As usual, the reason of this breakage is quite silly: in do_entIF, we
are checking for PS == 0 to see whether it was a kernel BUG() or
userspace trap.

It works, unless BUG() happens in interrupt - PS is not 0 in kernel mode
due to non-zero IPL, and the things get messed up horribly then.  In
this particular case it was BUG_ON(!irqs_disabled()) triggered in
run_posix_cpu_timers(), so we ended up shooting "current" with the
bursts of one SIGTRAP and three SIGILLs on every timer tick.  ;-)

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/alpha/kernel/traps.c b/arch/alpha/kernel/traps.c
index fd7bd17cc960..6f509a644bdd 100644
--- a/arch/alpha/kernel/traps.c
+++ b/arch/alpha/kernel/traps.c
@@ -240,7 +240,7 @@ do_entIF(unsigned long type, struct pt_regs *regs)
         siginfo_t info;
         int signo, code;
 
-        if (regs->ps == 0) {
+        if ((regs->ps & ~IPL_MAX) == 0) {
                 if (type == 1) {
                         const unsigned int *data
                           = (const unsigned int *) regs->pc;